Update some miscellaneous project files

.gitattributes

@@ -0,0 +1,21 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Include Markdown files in GitHub's file statistics for this repo.
+*.md linguist-detectable
+
+# Exclude config files from GitHub's file statistics. Most are YAML files and
+# Linguist already treats .yaml files as data, so only add some exceptions.
+.markdownlintrc linguist-documentation
+.shfmt          linguist-documentation

.github/SECURITY.md

@@ -1,19 +1,25 @@
 # Reporting security issues
 
-The ReCirq developers and community take security bugs in ReCirq seriously.
-We appreciate your efforts to responsibly disclose your findings, and will make
-every effort to acknowledge your contributions.
+This project's developers and community are committed to addressing security
+bugs promptly and effectively. We appreciate your efforts to disclose your
+findings responsibly, and will make every effort to acknowledge your
+contributions.
 
 Please **do not** use GitHub issues to report security vulnerabilities; GitHub
 issues are public, and doing so could allow someone to exploit the information
-before the problem can be addressed. Instead, please use the GitHub ["Report
-a Vulnerability"](https://github.com/quantumlib/recirq/security/advisories/new)
-interface from the _Security_ tab of the ReCirq repository.
+before the problem can be addressed. Instead, please use the *Report a
+vulnerability* interface from the *Security* tab at the top of this GitHub
+repository page.
+
+<div align="center">
+<img width="75%" alt="Location of the report button on the repository page"
+    src="./report-vulnerability-button.png">
+</div>
 
 Please report security issues in third-party modules to the person or team
-maintaining the module rather than the  project stewards, unless you
-believe that some action needs to be taken with ReCirq in order to guard
-against the effects of a security vulnerability in a third-party module.
+maintaining the module rather than this project's stewards, unless you believe
+that some action needs to be taken specifically with this project in order to
+guard against the effects of a security vulnerability in third-party software.
 
 ## Responses to security reports
 
@@ -27,4 +33,4 @@ announcement, and may ask for additional information or guidance.
 Please contact the project stewards at Google Quantum AI via email at
 [email protected] if you have questions or other concerns. If
 for any reason you are uncomfortable reaching out to the project stewards,
-please email [email protected].
+please email [email protected] instead.

.gitignore

@@ -39,3 +39,6 @@ docs/generated
 
 # Default pycharm virtual env
 .venv/
+
+# File created by write-ci-requirements.py
+ci-requirements.txt